Abstract A series of catalysts with different core‐shell structures has been successfully prepared by a hydrothermal method. They consisted of CeCoO x @TiO 2 (single shell), CeCoO x @Nb 2 O 5 (single shell) and CeCoO x @Nb 2 O 5 @TiO 2 (double shell) core‐shell nanocages and CeCoO x nanocages, in which CeCoO x was the core and TiO 2 and Nb 2 O 5 were shells. The influence of the core‐shell structure on the catalytic performance of o ‐dichlorobenzene was investigated by activity, water‐resistance, and thermal stability tests as well as catalyst characterization. The temperatures corresponding to 90 % conversion of o ‐dichlorobenzene ( T 90 ) of CeCoO x , CeCoO x @TiO 2 , CeCoO x @Nb 2 O 5 , and CeCoO x @Nb 2 O 5 @TiO 2 catalysts were 415, 383, 362 and 367 °C, respectively. CeCoO x @Nb 2 O 5 exhibited excellent catalytic activity, mainly owing to the special core‐shell structure, large specific surface area, abundant activity of Co 3+ , Ce 3+ , Nb 5+ , strong reducibility, and more active oxygen vacancies. It can be seen that the Nb 2 O 5 coating can greatly improve the catalytic activity of the catalyst. In addition, due to the protective effect of the TiO 2 shell on CeCoO x , CeCoO x @Nb 2 O 5 @TiO 2 catalysts exhibited outstanding thermal and hydrothermal stability for 20 hours. The T 90 of CeCoO x @Nb 2 O 5 @TiO 2 was slightly lower than that of CeCoO x @Nb 2 O 5 , but it had higher stability and hydrothermal stability. Furthermore, possible reaction pathways involving the Mars‐van‐Krevelen (MvK) and Langmuir‐Hinshelwood (L−H) models were deduced based on studies of the temperature‐programmed desorption of O 2 (O 2 ‐TPD), X‐ray photoelectron spectroscopy (XPS), and in situ diffuse reflectance FTIR spectroscopy (DRIFTS) characterization.
Enhancing chlorine and water resistance and suppressing by-product generation are crucial issues in the catalytic degradation of CVOCs. In this paper, surface acid modified (sulfurized and phosphorized) CoMnOx rhombic dodecahedra catalysts were synthesized for the deep destruction of o-DCB. The strong interaction between Co and Mn in the acid-modified CoMnOx stimulated the efficient production of active Co3+, Mn4+ and oxygen species, which considerably promoted C-H bond and C-Cl bond cleavage, significantly enhancing the activity of CoMnOx. Furthermore, we found that acid sites of the prepared CoMnOx-TAA materials effectively inhibited by-product formation and were highly selective for HCl. More importantly, CoMnOx-TAA exhibited excellent water and chloride resistance. EPR characterization confirmed a significant increase in the number of oxygen vacancies after acid modification . TPD indicated that the modified catalyst possessed abundant weak and medium acid sites. This work provides promising candidates and new insights into the industrial catalytic degradation of o-DCB.
Manganese-based catalysts had been considered as ideal alternative catalysts for selective catalytic reduction of NOx with NH3 due to their good potential for NOx removal, but their weak water resistance limited industrial applications. In order to improve the water resistance of low-temperature Mn-based catalyst in NH3-SCR reaction, Ti-OMS-2 catalyst was prepared by hydrothermal method, and polytetrafluoroethylene (PTFE) powder was methodically introduced on the catalyst surface by impregnation method. Importantly, the introduction of PTFE on the Ti-OMS-2 catalyst surface could effectively inhibit the adsorption of water molecules and reduce the probability of active species being consumed. Thus, it showed better catalytic activity and water resistance. The activity of Ti-OMS-2-20%-PTFE catalyst could reach more than 80% when water vapor was introduced at 180 oC. More importantly, Ti-OMS-2-20%-PTFE catalyst did not readily bind the active species (Mn4+, Mn3+ and Oads) and maintained the adsorption and activation of NH3 species. Moreover, PTFE of the Ti-OMS-2-20%-PTFE catalyst was easy to form a weak surface hydrophobic layer on the catalyst surface which could effectively inhibit water toxicity. Therefore, this work provided a new idea and experimental accumulation for the industrial application of Mn-based catalysts.
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